Evidence for neural re-use hypothesis from the processing of Chinese emotional words

Abstract

<p id="p00005">The two main theoretical views of emotional word processing are conflicting. According to standard psycholinguistics, emotions are elicited within the reading network itself after semantic activation. However, neural reuse theories suggest that emotional words can be directly processed by the brain region that is activated in emotional information processing, similar to how emotional images, smell, and faces are processed. This means that emotional effects to words occur before semantics, which benefits human adaptability. The processing of emotional words in phonetic characters supports the view of neural reuse, but the processing of emotional words in ideographic texts has no evidence. An event-related potential experiment and a behavioral experiment were conducted to explore the processing of emotional information while reading at an implicit level. <p id="p00010">A total of 262 Chinese words were selected from the Chinese Affective Stimulus System. Among these words, 128 were disgust-related words, 100 were neutral words, and 34 were transportation-related words. We then selected 35 neutral words, 35 disgust-related words, and 24 transportation-related words that were matched on the basis of valence and arousal. Twenty Chinese college students (10 female) participated in the EEG experiment. They were asked to press the response button using their right index finger when the words they read were related to transportation (Go trials). Otherwise, they should not respond (No-go trials). Another 30 healthy individuals (15 female) participated in the behavioral experiment. However, they were asked to silently read the presented words and press the response button using their right index finger only when a given word was not related to transportation (Go trials). Otherwise, they should not respond (No-go trials). <p id="p00015">The EEG experiment showed that differences between disgust and neutral words appeared as early as 170 ms after the onset of stimulus. No significant effect of emotion was found on P100 (the early ERP component). However, a significant main effect of emotion was found for the early posterior negativity (EPN). Disgust-related words evoked a larger right EPN than neutral words did. A negative going wave reflecting the processing of meaning was found at approximately 400 ms, and source localization indicated a cortical generator of emotion effect near the left anterior insula. The inhibition response to disgust-related words generated greater late positive component than the response to neutral words. Specifically, disgust-related words evoked a much larger P600 amplitude compared with neutral words. Behavioral experiment results showed a significant difference between the reaction time to disgust-related words and neutral words. Participants responded faster to disgust-related words than to neutral words. <p id="p00020">Results indicate that negative emotional words have an advantage in processing over neutral words. Emotional response to negative emotional words occurs before the processing of their semantics. The processing of negative emotional words supports theory of neural reuse. This finding shows that the nervous system is highly flexible and can process information in an appropriate manner according to the needs in an actual situation. Moreover, when processing emotional information, ideographic Chinese emotional words start earlier and activate a wider range of brain regions than phonetic Western emotional words.